Re: IfExpr has a mandatory else clause

Appreciate the clarification.

However making the else clause optional does not make the
IfExpr expression less of an expression does it ?
Implicitly returning an empty sequence in the absence of an
else clause is not intuitive ?

----- Original Message ----- 
From: "Kay, Michael" <[email protected]>
To: "TAN Kuan Hui" <[email protected]>; "Bas de Bakker"
<[email protected]>; <[email protected]>
Sent: Monday, January 26, 2004 7:38 PM
Subject: RE: IfExpr has a mandatory else clause



> So is grammar ambiguity the reason that IfExpr has a
> mandatory else clause ? Are there other design considerations

Making the else clause mandatory emphasizes that this is an expression
and not a procedural statement: it always returns a result. In most
languages where I've seen a conditional expression, both branches are
mandatory.

An exception of course is <xsl:if> in XSLT, but perhaps that's because
the semantics have only recently been recast into expression form, and
the spec still talks of this as an "instruction" rather than an
"expression".

Michael Kay